Vacuum lift apparatus with a control valve assembly

ABSTRACT

A lift truck attachment for lifting heavy loads through use of negative air pressure characterized by a novel valve structure responsive to load engagement for opening the negative air pressure line.

United States Patent 1191 1111 3,923,177

Horton 1 1 Dec. 2, 1975 1 1 VACUUM LIFT APPARATUS WITH A 3.152.828 10/1964 Lytle 294/64 R CONTROL VALVE ASSEMBLY 3.187.989 6/1965 Barto 214/650 3.206.041 9/1965 McGrath... 214/() SC- 1 1 Inventor: Earl Horton, Philadelphia, Pa. 3219.380 11/1965 0161155 294/64 A' I 3.314.559 4/1967 Horton 294/65 [73] Assignee. Little Giant Products, Inc., Peona, 3318A 5/1967 Olson u 314/650 56 3,322.454 5/1967 Mindrum 214/650 50 22] Filed: June 21 973 3361.280 1/1968 Traver 294/65 21 Appll 372 393 FOREIGN PATENTS OR APPLICATIONS 1,921,513 4/1971 Germany 294/65 [521 US. Cl. 214/650 8G1 294/64 R 4 1511 1111.01 B65g 47/00; B66f 9/18 f f W [581 Field of Search 214/650 s0, 1 BS, 1 BT, Amsmn' 3101mm" 214/1 BH, 1 EV; 294/64 R, 65; 251/324-325 [57] ABSTRACT [56] References Cited A lift truck attachment for lifting heavy loads through UNITED STATES PATENTS use of negative air pressure characterized by a novel 1,294,103 2/1919 Hitchcock 294/64 R valve structure responsive to load engagement for 2,253,283 8/1941 Minaker 294/65 opening the negative air pressure line. 2,578,220 12/1951 Bi11ner.... 294/65 3,147,872 9/1964 015011 214/650 50 3 Clalms, 8 Drawlng Flgures US. Patent Dec. 2, 1975 Sheet 1 of 3 3,923,177

US. Patent Dec. 2, 1975 Sheet20f3 3,923,177

US. Patent Dec.2,1975 sheet om 3,923,177

VACUUM LIFT APPARATUS WITH A CONTROL VALVE ASSEMBLY This invention relates to improvements in attachments for industrial lift trucks and is more particularly concerned with the novel construction and assembly of apparatus for engaging and lifting heavy loads by means of vacuum pads, and to the novel construction of the vacuum load-sensing valve assembly.

Various structures have been devised which include vacuum pads for engagement by the load. Usually such structures are formed as an integral part of a lift truck assembly and have numerous structural and operational disadvantages. For example, when made an integral part of the lift truck assembly, such a truck is not serviceable for other uses and also all known vacuum type load lifting assemblies require manual operation of the control valves to create the necessary vacuum in the pads when a load is engaged. Other known valve controls for such lift mechanism includes valve actuating mechanism that is outside the valve proper and consequently such mechanisms are subject to damage by improper use or engagement by the load. One such structure is depicted in Horton US. Pat. No. 2,942,745, dated June 28, 1960. Frequently, because of misalignment of the load, an exterior located control may be actuated before the full load contact by the pads is effected. As a result, there is a loss of vacuum, which is wasteful, time consuming and which can be hazardous.

The present invention includes a novel vacuum load sensing valve assembly which functions automatically to open the line to the vacuum source when a load is engaged, so that there can be no premature or erroneous manipulation of the valve.

It is therefore an object of the present invention to provide novel means for mounting a plurality of load engaging pads on an industrial lift truck.

Another object is to provide novelly constructed vacuum pads of a type incorporating novel automatically actuated load sensing valves.

Another object is to provide a novelly constructed vacuum load sensing valve.

Another object is to provide a novelly constructed load lifting mechanism for lift trucks which is not difficult or too expensive to manufacture, and which is easy to operate and positive in its operation.

Other objects and advantages of the invention will become apparent with reference to the following description and accompanying drawings.

IN THE DRAWINGS FIG. 1 is an elevational view of an industrial lift truck having the pads and valves embodying the invention mounted thereon.

FIG. 2 is a horizontal plan view of the pad-valve mounting assembly.

FIG. 3 is a front elevational view of the pad-valve assembly as viewed along line 3 3 of FIG. 1.

FIG. 4 is a horizontal central sectional view of one of the pad-valve assemblies, taken substantially on line 4 4 of FIG. 3.

FIG. 5 is an enlarged axial sectional view of the valve assembly, showing the valve closed.

FIG. 6 is a view similar to FIG. 5, showing the valve open.

of valve, showing it closed.

FIG. 7 is a central sectional view of a modified form FIG. 8 is a view similar to FIG. 7, showing the valve open.

Referring now to the exemplary disclosure of the invention as shown in the accompanying drawings, there is illustrated in FIG. 1 a representative industrial truck 11 supported on front and rear wheels, 12 and 13, respectively. The truck is equipped with primary uprights 14 in which a mast 15 is guided for vertical movement. The mast mounts for vertical movement a carriage 15a which has a pair of forwardly projecting bearing brackets 16 having a vertically disposed pivot pin 17 journalled therein and extending between said brackets. The pivot pin affords a swivel mounting for a pair of horizontally disposed arms 18 which are vertically spaced apart as shown.

The arms 18 each carry on each of their ends a load engaging assembly generally indicated at 19. In the present disclosure, these assemblies are designed to be engaged with a cylindrical load, such as a roll or rolls of newsprint 21. It will be observed upon reference to FIG. 3, that there are two sets of vertically aligned load engaging assemblies 19, so as to adapt the assembly to lift one, two, three or four rolls of paper, determined by the size thereof.

' More specifically, each load engaging assembly 19 consists of a curved, articulated steel plate 22 covered with a slip-on type ribbed rubber pad 23. Extending rearwardly from the plate 22 is an arched web 24 that is pivotally mounted, as at 25, to the related end of the associated arm 18. The ribbed concave surface of the pad has ribs 26 thereon and a perimeter flange 27 (see FIG. 4) of sufficient width or depth as to contact the load before the ribs contact the same for a purpose to be understood and described presently. The ribs 26 prevent the load from having total surface contact therewith and accordingly insures the presence of paths between the ribs for the flow of atmosphere during use.

Each pad assembly has centrally located therein, and preferably welded thereto, a valve assembly 28 which is in flow communication with a source 29 of negative pressure or vacuum through a conduit 31. The valve, described in detail hereafter, is of a type to be normally spring biased into closed position, but which is opened when a load is properly positioned relative to the pad for lifting. When the valve is open, negative pressure is built up between the pad and the engaged load to a sufficient degree to secure the load firmly to the pad, whereupon it may be lifted and moved. After the load is repositioned, the load is released by manual valve means controlled by the operator which is effective to cut off the negative pressure to the pad.

Referring now to FIGS. 5 and 6, the valve assembly 28 is comprised of a housing 32 having an axial bore 33 therein terminating at one end in an internally threaded enlarged diameter 34. A closure plug 35 is threaded into the threaded diameter 34 and the other end of the housing is externally flanged, as at 36. The valve housing 32 is secured to the metal plate 22 with its forward flanged end projecting through an opening therein.

With the pad 23 in place on plate 22, a clamp plate 37 is laid over the pad margin and is secured to the housing 32 as by screws 38.

A plunger valve stem 39 slidable in the axial bore 33 normally has its forward rounded tip projecting beyond the flanged end 36 of the housing by reason of a compression spring 41 arranged between the recessed rear end 42 of the stem and the plug 36. The axial bore 33 has a pair of annular channels 43 and 44 therein. The

3 channel 43 has communication through a flow passage 45 with the conduit 31, whereas the channel 44 is in communication at all times with an elongated annular recess 46 on the surface of the valve stem 39.

When the valve stem 39 is in the valve closing position shown in FIG. 5, the rear end of the valve stem is in register with the channel 43 and is effective to cut off negative pressure through the valve. When a load is contacted by the forward rounded end of the valve stem 39, said stem is depressed against the action of spring 41, so as to carry the annular recess 46 on said stem into register with the annular channel 43, as shown in FIG. 6. Since the recess 46 is still in registering alignment with the channel 44, negative pressure from channel 43 flows into channel 44 and then through aligned ports 47 and 48, into the space between the pad 23 and the engaged roll 21.

It will be appreciated that only the valves in plate pad assemblies contacted by a load are opened. Thus, when a small roll is to be picked up, only the pad assembly engaged thereby will be activated, the remaining pad assemblies having their valves remaining closed. Also, because the valve is opened by contact with its valve stem 39, there is no possibility of the valve being actuated by a misaligned load, because to depress the valve stem the load must be centered on the pad assembly.

FIGS. 7 and 8 depict a modified form of contact valve wherein like numerals are used to identify corresponding parts. As shown, the valve housing 51 has an axial bore 52 through which the valve stem 53 projects. A plate 54 secures the metal plate 22 and its rubber pad 23 to the housing. The axial bore 52 is enlarged at the rear end of the housing, as at 55, and a cover plate 56, secured by screws 57, seals the rear end of the bore. The valve stem 53 has an external flange 58 on its rear end that operates in the enlarged bore 55, and which is faced with an o-ring 59 adapted, when the valve is closed (as shown in FIG. 7) to seat on the face 61 of the housing in bore 55 to close a port or ports 62, leading to the face of the pad 23. When the stem 53 is depressed upon being contacted by a load, the flange 58 and its o-ring 59 are carried rearwardly (as shown in FIG. 8) so as to afford a flow passage between the exhaust line 31, a bore 63, bore 55 and port 62, to

4 thereby cause evacuation of the space between the pad 23 and the load.

It should be quite evident that applicant has provided a vacuum roll handler that is automatic in its operation insofar as its load gripping capabilities are concerned; and that there is provided novel valve means to control the exhaust of atmosphere from between the load holders or pads and the load.

Although I have described preferred embodiments of the invention in considerable detail. it will be understood that the description thereof is intended to be illustrative and not restrictive, as details of the structure may be modified or changed without departing from the spirit or scope of the invention. Accordingly, I do not desire to be restricted to the exact construction described and shown.

I claim:

1. A vacuum controlled load lifting system comprising a mast assembly including a carriage mounted on a lift truck for vertical lifting movement, a plate mounted on the carriage, a resilient vacuum pad having a load contacting surface mounted on the front face of said plate, a valve body mounted on the back face of said plate, an axial bore in said body, a closure for one end of said bore, conduit means connecting said bore with a source of negative air pressure, a passageway in said body spaced from and parallel to said bore opening at one end onto the vacuum pad load contacting surface and having its other end communicating with the bore, a valve stem in said bore, and spring means between said closure and valve stem normally holding the valve stem in position to cut off the supply of negative air pressure to the passageway and with its forward end projecting through and beyond the plane of the load contacting surface, said valve stem being depressed upon contact with a load to connect the passageway with the conduit means.

2. The system recited in claim 1, wherein the pad has ribs and channels on its load engaging face to facilitate the creation of a vacuum over its entire engaging face when the valve is open.

3. The system recited in claim 1, wherein the valve is centrally located on the pad plate assembly. 

1. A vacuum controlled load lifting system comprising a mast assembly including a carriage mounted on a lift truck for vertical lifting movement, a plate mounted on the carriage, a resilient vacuum pad having a load contacting surface mounted on the front face of said plate, a valve body mounted on the back face of said plate, an axial bore in said body, a closure for one end of said bore, conduit means connecting said bore with a source of negative air pressure, a passageway in said body spaced from and parallel to said bore opening at one end onto the vacuum pad load contacting surface and having its other end communicating with the bore, a valve stem in said bore, and spring means between said closure and valve stem normally holding the valve stem in position to cut off the supply of negative air pressure to the passageway and with its forward end projecting through and beyond the plane of the load contacting surface, said valve stem being depressed upon contact with a load to connect the passageway with the conduit means.
 2. The system recited in claim 1, wherein the pad has rIbs and channels on its load engaging face to facilitate the creation of a vacuum over its entire engaging face when the valve is open.
 3. The system recited in claim 1, wherein the valve is centrally located on the pad - plate assembly. 